The present invention concerns novel ether derivatives of 2,5-dimercapto-1,3,4-thiadiazoles and their use as multifunctional additives in lubricating compositions.
Lubricating compositions ordinarily are formulated with various additives to enhance their performance. A problem sometimes encountered is that of compatibility between the various additives used. Therefore, it is desirable to use lubricating additives that can perform different functions.
Generally, lubricants contain additives known as antiwear agents which increase the load-carrying capacity of lubricants. The antiwear additives promote the formation of a surface film and thereby prevent wear of the contacting metal surfaces. During the course of use, lubricants are susceptible to deterioration due to oxidation. The oxidative process leads to the loss of lubricating properties and inadequate protection of the device to be lubricated. Antioxidants are added to inhibit the oxidative process. Therefore, it is desirable that antiwear agents possess antioxidant properties.
The most commonly used additives possessing both antiwear and antioxidant properties are zinc dihydrocarbylphosphorodithioates and heavy metal dihydrocarbyldithiocarbamates. However, due to stricter environmental controls, it is particularly desirable to reduce the phosphorus and heavy metal content in lubricants. There is a need to develop improved lubricating compositions that are environmentally sound. German Pat. No. 943,790 describes ashless 1,3,4-thiadiazole derivatives that improve the film strength under high load.
It has been surprisingly discovered that the foregoing disadvantages of the prior art lubricants can be eliminated by replacing all or part of the metal additives with certain ashless multifunctional ether derivatives of 2,5-dimercapto-1,3,4-thiadiazoles.